Rock drill



Dec. 31,1957

C. D. GRABER ROCK DRILL Filed April 23, 1954 0 26 I il A "Tri INVENToR. Cwrb D. rber BY l y ATTRIVEYS United States Patent hice ROCK DRILL Carl D. Graber, Orrvlle, Ohio Application April 23, 1954, Serial No. 425,135

3 Claims. (Cl. 287-125) The invention relates to rock drills of the type comprising a drill rod or stem and a bit detachably connected thereto, and more particularly to means for coupling the drill bit to the stem.

An object of the invention is to provide means for coupling the drill bit to the stem in such a manner that it will not work loose during operation.

Another object is to provide such coupling means comprising a continuously threaded stud received in threaded sockets in the drill bit and stem, the portion of the stud received in the stem being tapered.

A further object is to provide such a device in which the threaded stud has an -unthreaded pilot portion received in the bore ofthe drill bit or point.

A still further object is the provision of means whereby the pilot portion of the lstud has a tight t in the sides and bottom of the bore in the vdrill bit or point.

Another object is to provide such a device in which the pilot end portion `of the threaded stud is split and means is provided for expanding the same into the bore in the drill bit or point.

A further object is to provide such a construction in which the threaded stud has a threaded axial bore terminating in an unthreaded tapered end within the split portion of the stud to receive a threaded expanding pin having `a tapered, Unthreaded end portion for expanding the `split pilot portion of the stud.

The above objects together with others which will be apparent from the drawing and following description, or which may be later pointed out, may be attained by constructing t-he improved rock drill in the manner hereinafter described in detail and illustrated in the accompany, ing drawing, in which:

Fig. l is a side elevation of a drill bit and the adjacent end portion of the stem with coupling means embodying the invention;

Fig. 2 a longitudinal, `sectional view through the stem and adjacent portion of the drill bit, showing the manner in which the pilot portion of the coupling stud is expanded within the bore of the drill bit or point;

Fig. 3 an end elevation of the drill bit;

gig. 4 a detached, side elevation of the coupling stud; an

Fig. 5 a detached, side elevation, with parts broken away, of the expanding pin.

Referring now more particularly to the construction illustrated, in which similar numerals refer to similar parts throughout, a portion of a stem or drill rod is indicated at and the drill bit or point is indicated generally at 11.

The drill bit or point 11 may be of the general shape best shown in Figs. l and 2, being flared downwardly and outwardly from the stem as indicated at 13 and provided with a plurality of cutting edges 14.

If desired, a reduced central extension 13a may be formed upon the lower end of the drill bit or point and provided with the cutting edges 14a. However, it should be understood that the particular shape of the drill bit or Patented Dec. 31, 1957 point may vary, the invention residing in the coupling means for coupling the drill bit or point to the stem rather than in the specific shape of the drill bit per se.

The stem or rod 11 has an upwardly tapered, axial, threaded socket 15 in its lower end to receive the threaded, conical portion 16 of the coupling stud which is indicated generally .at 17.

The lower portion 18 of the stud is straight or cylindrical and terminates at its lower end in a reduced' unthreaded pilot portion 19 having a at lower end. With the exception of this pilot portion 19, the stud 17 is threaded continuously throughout its length.

A threaded, faxial bore 20 extends from the upper end of the stud 17 to a point near the lower end thereof, terminating at its lower end in the tapered, Unthreaded portion 21. The lower, straight portion 18 of the stud, including the pilot portion 19 thereof, is provided with one or more radial slots, as indicated at 22, extending from the central bore in the stud through the periphery thereof.

A threaded, axial bore 23 is provided in the upper end portion of the drill bit or point 11, terminating at its lower end in the -reduced Unthreaded portion 24, shaped to receive t-he threaded, cylindrical lower portion 18 of the stud 17 and the reduced unthreaded pilot portion 19 thereof, respectively.

In assembling the drill bit or point upon the stem, the cylindrical lower portion 18 of the stud 17 is screwed into the threaded bore 23 in the drill bit or point, the unthreaded reduced pilot portion 19 of the stud being in close contact with the flat bottom wall 25 of the bore, as best shown in Fig. 2.

The threaded expanding pin 26 is then yscrewed down into the axial bore 20 of the coupling stud 17, the unthreaded, frusto-conical lower end 27 thereof being received in the Unthreaded conical lower end 21 of the bore so as to expand the split lower portion 18 of the stud tightly into the threaded socket 23 of the drill bit or point.

This expanding pin is in the form on `an Allen head screw, having the hexagonal socket 28 in its upper end to receive an Allen head screw driver for manipulating the same.

It will be seen that after this expanding pin has been tightly screwed into place within the coupling stud 17, the lower portion 18 of the stud 17 will be fitted tightly within the socket 23 in the drill bit or point so that there can be no relative movement of the drill bit and stud either longitudinally or laterally.

The stem 10 is then screwed tightly onto the tapered upper end portion 16 of the coupling stud, the lower flat end of the stem tightly contacting the upper flat end of the drill bit or point as at 29.

The drill bit or point will thus be tightly coupled to the stem, thus eliminating any possibility of either end or side movement of the drill bit or point relative to the coupling stud, preventing the drill bit from working either sideways or endways on the threads.

In the foregoing description, certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiments of the improved construction illustrated and described herein are by way of example, and the scope of the present invention is not limited to the exact details of construction.

Having now described the invention or discovery, the construction, the operation, and use of preferred embodiments thereof, and the advantageous new and useful results obtained thereby; the new and useful construction, and reasonable mechanical equivalents thereof obvious to art, are set forth in the appended ng a stem having a conical threaded eof, a coupling stud having a conical i in the conical socket in the stem l portion having a flat end, said stud hreaded throughout the conical poral portion, the cylindrical portion of radially, a separable drill bit having et therein provided with a lat inner e lcylindrical portion of the stud with tud in conta-ct with the at end wall being an axial threaded bore in the ion of the stud, and a threaded exaid threaded axial bore and having a aded end portion for expanding said ion of the stud within the threaded itudinal force will not produce relareaded coupling parts.

ing a stem having a conical threaded cof, a coupling stud having a conical u in the conical socket in the stern i portion terminating in a reduced unn having a at end, said stud being d throughout the conical portion and n, the cylindrical portion of the stud s separable drill bit having a threaded terminating in an Unthreaded reduced th a ilat inner end wall receiving the of the stud with the reduced unn thereof located in said unthreaded said socket with the flat en-d of the the dat end wall of the socket, there ded bore in the stud terminating in a i tapered Unthreaded end within the said threads having a slight enough tapered unthreaded end within the split cylindrical portion of the stud, and a threaded expanding pin Within said threaded axial bore and having a frusto-conical unthreaded end portion for expanding 'said split cylindrical portion Iof the stud Within the threaded socket in the drill bit, said threads having a slight enough pitch so that a longitudinal force will not produce relative rotation of the threaded coupling parts.

3. A drill `comprising a stem having a conical threaded socket in an end thereof, a coupling stud having a conical end portion received in the conical socket in the stem and a cylindrical end portion terminating in an Unthreaded reduced pilot portion, the stud being continuously threaded throughout the conical portion and the cylindrical portion, the cylindrical portion of the stud being split radially, a separable drill bit having a threaded axial socket therein terminating in an Unthreaded reduced portion provided with a lat inner end wall receiving the cylindrical portion of the stud with the reduced pilot portion of the stud located in the reduced portion of the socket and the flat end of said pilot portion in contact with the flat end wall of the socket, and means for expanding the split cylindrical portion of the stud within the threaded socket in the drill bit, said threads having a slight enough pitch so that a longitudinal Iforce will not produce relative rotation of the threaded coupling parts.

References Cited in the le of this patent UNITED STATES PATENTS 104,576 Good June 21, 1870 1,054,181 Davenport Feb. 25, 1913 1,879,856 Peterson Sept. 27, 1932 2,005,498 Hart June 18, 1935 2,463,859 Engstrom Mar. 8, 1949 2,569,275 Baker Sept. 25, 1951 2,608,103 Shonnard et al. Aug. 26, 1952 

